1. Field of the Invention
The present invention relates to an image forming apparatus and a paper feed control method for an image forming apparatus. More particularly, the present invention relates to an image forming apparatus capable of paper feed control while accurately detecting the weight of each sheet of paper stored in a paper storage part or the weight per unit number of sheets stored therein and further capable of judging, for example, whether or not the number of sheets remaining in the paper storage part is adequate for the designated number of copies to be made, and of displaying the result of the judgment. The present invention also relates to a paper feed control method for such an image forming apparatus.
2. Description of the Related Art
In the conventional image forming apparatus of the type described above, the detection of the remaining quantity of copying paper held in a paper storage part (paper feed cassette) cannot very accurately be performed. For example, the invention disclosed in Japanese Patent Application Unexamined Publication (KOKAI) No. Hei 10-148982 detects the amount of upward movement of the paper storage part by counting the number of motor pulses. On the other hand, the number of images formed is counted with a paper counting means to calculate the amount of upward movement per unit number of sheets of paper, and the number of remaining sheets is calculated from the amount of upward movement left.
The above-described conventional image forming apparatus uses the motor pulses to calculate the remaining quantity of paper. However, it is not easy to make the motor pulse accuracy correspond to the thickness of thin paper. The accuracy degrades particularly when sheets of paper different in thickness are used mixedly or when the reverse sides of used sheets are used, by way of example. When the accuracy of the calculation of the remaining quantity of paper is low, a problem may occur when the user leaves the place where the image forming apparatus is placed after setting and executing a copying operation for making a large number of copies. That is, when the user returns to the place, the desired copying operation may have undesirably been suspended because of a lack of paper.